Reference is made to U.S. Pat. Nos. 5,126,581, 5,696,580, 7,999,936, 7,105,849, and DE 10 2008 007 743.
For analyzing a fluidic sample, the fluidic sample may be filled into a sample container. An electromagnetic radiation beam may then be brought in interaction with the fluidic sample, wherein the scattered electromagnetic radiation beam may then carry information indicative of physical and/or chemical properties of the fluidic sample. Such an arrangement may be used for determining the particle size by dynamic light scattering (DLS).
By DLS, particle sizes in dispersions may be determined. An advantage of the DLS method is that only a very limited knowledge with regard to the properties of the sample is sufficient. However, the value of the refraction index of the sample (in particular of the solvent thereof) and the viscosity thereof are required as input parameters. Hence, a user has to input manually in a DLS apparatus which refraction index a sample under investigation (in particular a solvent thereof) is used. For example, a user may use a database with values of the refraction index for frequently used solvents as a function of the measurement temperature. The user must select a solvent or must manually input a corresponding numerical value for the refraction index. The same applies to viscosity. However, it is possible to determine viscosity by DLS when all other parameters (i.e. also particle size) are known. The so-called Zetasizer from Malvern Instruments Ltd, which is commercially available, has an integrated method for determining viscosity which is also denoted as microrheology.
In view of the foregoing, the value of the refraction index or the used solvent must be known for DLS. When the solvent is however not known, not available in a database, or is strongly temperature-dependent, it is necessary for a user to first measure the refraction index with a separate device, for instance with the so-called refractometer Abbemat of Anton Paar GmbH.
A further shortcoming of conventional DLS apparatuses is that, for example as a consequence of a long-term drift of the DLS apparatus, the latter may drift out of a desired operation condition under which a measured intensity of a detection signal has a pronounced value. This may result in a deterioration of the measurement accuracy or requires a user in a cumbersome way to readjust the value manually.
Concluding, there is still room for improving accuracy of conventional DLS apparatuses. Moreover, there is still room for improving user-convenience when operating DLS apparatuses.